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<title>GrADS Function: tcorr</title>
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<h2><b>tcorr()</b></h2>
<p>
<code>tcorr (<i>expr1, expr2, tdim1, tdim2</i>)</code>

<p>
This function produces a spatial map of temporal correlation
coefficients. 

<p>
<ul>
<code><i>expr1</i>&nbsp;&nbsp;&nbsp;</code>- 
a valid GrADS expression that varies in time<br>
<code><i>expr2</i>&nbsp;&nbsp;&nbsp;</code>- 
a valid GrADS expression that varies in time and may also vary in X and Y<br>
<code><i>tdim1</i>&nbsp;&nbsp;&nbsp;</code>- 
starting time dimension expression <br>
<code><i>tdim2</i>&nbsp;&nbsp;&nbsp;</code>- 
ending time dimension expression <br>
</ul>

<p>
The <code><i>expr1</i></code> time series is correlated to the time
series at each grid point in <code><i>expr2</i></code>. The result is
a grid of correlation coefficients that matches the X and Y dimensions
of <code><i>expr2</i></code>.

<p>
<h3>Usage Notes</h3>
<ol>
<li>If both <code><i>expr1</i></code> and <code><i>expr2</i></code>
vary only in time, the output is a single value.
<p>
<li>Use the <a href="gradfuncscorr.html"><code>scorr</code></a>
function to do correlation over the spatial domain.
</ol>

<p>
<h3>Example</h3>
<ol>
<li>
This example calculates the temporal correlation between sea level pressure
and the defined variable elnino, an areal average of surface temperature 
in the equatorial Pacific.
<p>
<pre>
set x 1
set y 1 
set z 1 
set t 1 100
define elnino = aave(ts,lon=-160,lon=-80,lat=-10,lat=10)
set lon -180 180
set lat -90 90
set z 1
set t 1
d tcorr(elnino, slp, t=1, t=100)
</pre>
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